1. Field of the Invention
The present invention is directed to an extracorporeal lithotripsy apparatus, and in particular to such an apparatus including means for laterally adjusting the position of the focus region so that a calculus which has been laterally displaced from an initial position can still be maintained within the focus region for effective disintegration.
2. Description of the Prior Art
Extracorporeal lithotripsy devices are known in the art which include a shock wave source for generating a shock wave in a shock wave transmitting medium, with the shock wave being focused at a focus region. The apparatus is initially positioned so that the focus region is coincident with a calculus to be disintegrated in the body of a patient. Devices of this type are used in medicine, for example, to disintegrate gallstones and kidney stones. The use of these devices is advantageous because a surgical operation or the use of invasive probes are not required, and therefore injury to the patient and the risk of infection are minimized.
An example of such an extracorporeal lithotripsy apparatus is described in German OS No. 33 280 39. The shock waves generated by a shock wave source are coupled into the body of a patient via medium which transmits the shock waves. In the body of the patient, the shock waves are focused, for example, onto a kidney stone and transfer a portion of their energy in the form of compressive and tensile forces, resulting in disintegration of the calculus. Focusing of the shock wave may be done, for example, with an acoustic lens. The focus region in the body of the patient can be displaced along the acoustic axis of the shock waves by displacing the acoustic lens along that same direction. The focus region can thus follow a change in the location of the calculus along the acoustic axes.
Due to respiration or other movement, however, the calculus may also change position transversely relative to the acoustic axis. In the conventional devices, the only way to adjust the position of the focal region to follow a transverse movement of the calculus is to transversely adjust the acoustic axis of the shock wave source. This requires that the shock wave source, or the housing containing the shock wave source, be mounted to permit universal pivoting of the shock source, together with the acoustic lens.
Due to the masses which must be moved, such lateral adjustment is very sluggish, so that the focus region can only be adjusted to accommodate relatively slow changes in the position of the calculus. Changes in the location of the calculus which are caused by respiration are relatively rapid, and a follow-up adjustment of the focus region, if possible at all, can only be accomplished with difficulty in a conventional device. If such a follow-up adjustment is not undertaken, the shock wave source can only be activated when the calculus is again situated in the focus region, thereby significantly lengthening the treatment time.
An ultrasound diagnostic apparatus is described in U.S. Pat. No. 3,913,061 wherein the ultrasound echoes, reflected by an examination subject, are focused onto a linear array and can be deflected along the linear array. The apparatus also includes two acoustic lenses by which the reflected ultrasound signals are focused on to the linear array. This ultrasound apparatus also includes two elements each having a wedge-shaped longitudinal section, which are mounted to be rotatable around a common axis in the region between the acoustic lenses. These elements are aligned transversely relative to the propagation direction of the ultrasound signals. The wedge-shaped elements are offset by 180.degree. relative to each other and are rotatable around the common axis with a drive mechanism in different rotational directions, but with the same angular speed. Upon rotation of the elements surround the common axis, the ultrasound signals reflected by the examination subject, and focused onto the linear array by the acoustic lens, are deflected along the linear array in oscillating fashion. The acoustic lenses and the wedge-shaped elements are disposed in a medium which transmits the ultrasound signals.